Massachusetts will become the 18th state to allow for the medical use of marijuana, starting January 1st 2013. NBC projects that Question 3 will win approval in the state. With 38.1 percent reporting, the measure is currently leading 62.8 percent yes to 37.2 percent no.

The newly approved initiative allows patients with a written certificate from their doctor to use medical marijuana. Patients will be allowed to possess up to a 60 day supply of marijuana for their medical needs. Patients and caregivers will be required to register with the state’s Department of Public Health.

In addition, the law will allow a limited number of treatment centers to grow, process and provide patients with their medical marijuana. In 2013 there can be no more than 35 such treatment centers in the entire state. All treatment centers will be required to be non-profits and must register with the state.

The initiative will take effect on the first day of 2013 but it may take longer for some aspects of the law to become fully operational.

Medical marijuana, while now legal under state law in 18 states plus the District of Columbia, is still technically illegal under federal law.